The Naked Scientists

The Naked Scientists Forum

Author Topic: Does gravity change in the centre of the Earth?  (Read 1797 times)

Assad Ali

  • Guest
Does gravity change in the centre of the Earth?
« on: 14/12/2010 10:30:03 »
Assad Ali asked the Naked Scientists:
   
Would the force of gravity change if you were to tunnel down into the Earth?

What do you think?
« Last Edit: 14/12/2010 10:30:03 by _system »


 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Does gravity change in the centre of the Earth?
« Reply #1 on: 14/12/2010 10:59:48 »
Yes, the force of gravity on you increases.
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Does gravity change in the centre of the Earth?
« Reply #2 on: 14/12/2010 11:04:15 »
Yes.

Obviously in the middle of the earth, one would have all the mass above a person and one would essentially be weightless (0 gravity).

According to the notes I found on the web, the earth is not a uniform density, and thus it was predicted that the highest gravity was predicted to be found at the Core/Mantle Boundary, of about 10.7 m/sē, at a depth of about 2885 km (note, it is about 9.8 m/sē at the surface).  As you descend further, the gravity would decrease to 0 in the middle.

http://www.chsfootball.net/earth_g_2.doc
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Does gravity change in the centre of the Earth?
« Reply #3 on: 14/12/2010 11:07:20 »
  As you descend further, the gravity would decrease to 0 in the middle.
Why zero and not infinity?
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Does gravity change in the centre of the Earth?
« Reply #4 on: 14/12/2010 12:33:19 »
We seem to get this question about once a week at present.  Clifford's answer that it diminishes in general is correct; I hadnt realised that specifically that due to non-uniformity actually goes up for a while.

C4Me - the reason it drops is, that presuming symmetry, one only feels attraction from the sphere 'inside' your position, everything outside your position cancels out.  Both Newton and Gauss proved this - the easist wiki/google search is on "Newtons Shell Theorem"
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Does gravity change in the centre of the Earth?
« Reply #5 on: 14/12/2010 12:46:05 »
C4Me - the reason it drops is, that presuming symmetry, one only feels attraction from the sphere 'inside' your position, everything outside your position cancels out.  Both Newton and Gauss proved this - the easist wiki/google search is on "Newtons Shell Theorem"
Oh yes, thanks for clearing that one imatfaal. I knew it was past my bed time :)
 

The Naked Scientists Forum

Does gravity change in the centre of the Earth?
« Reply #5 on: 14/12/2010 12:46:05 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums
 
Login
Login with username, password and session length